托卡马克中离子回旋共振加热下的磁化射频鞘的粒子模拟

In tokamak devices, ion cyclotron resonance heating (ICRH) can drive radio-frequency(rf) sheaths which may produce a number of unwanted interactions . Understanding the magnetized rf sheath induced by ICRH in a tokamak has been of significance for the controlling contamination of the core plasma, the extension lifetime of antenna and relevant component, and improvement of coupling efficiency of ion cyclotron wave with plasma. In this projection, the properties of magnetized plasma rf sheath containing energetic ions are examined by the particle-in-cell(PIC) method in plasma software VORPAL framework, combined with ICRH experimental results in EAST and theroy of rf sheath. As the important application of this model, impurity sputtering yield is calculated by using the empirical formulas based on the Sigmund's theroy, surface temperature of material is obtained by considering interaction among heat flux through the sheath at the material and material thermal response, the sheath power dissipation is understanded by discussion the sheath voltage-current relation. On the basis of the explanation of the experimental results associated with rf sheath during ICRH, we expore the effective impurity control approaching in ICRH, elaborate the resoan of hot spot on the surfaces of antenna and relevant component, and find out some new methods to reduce the sheath power dissipation. The simulation results provide a reference for the optimized antennna designs for EAST and anntenna designs for next reactor with ICRH.

在托卡马克装置中，离子回旋共振加热(ion cyclotron resonance heating, ICRH)引起的射频鞘会诱发一系列负面效应。数值模拟ICRH下的射频鞘，对控制芯部等离子体污染，延长天线和相关部件的材料寿命，提高波与等离子体的耦合效率有着重要意义。本项目利用粒子模拟软件VORPAL，结合ICRH实验结果和射频鞘的理论，研究ICRH时存在高能离子的磁化射频鞘的结构特性。然后根据基于Sigmund理论的经验公式计算杂质溅射产额；考虑横越鞘层打到材料表面的能流和材料相互作用，分析材料表面温度变化规律；通过讨论鞘层电流的伏安关系，理解鞘功率损耗。在解释ICRH中与射频鞘相关的实验现象基础上，探索控制高功率ICRH下杂质产生的有效措施，阐明在ICRH中天线相关部件表面形成热斑的原因以及寻找减少鞘功率损耗的方法，为EAST天线优化和今后反应堆利用ICRH时的天线设计提供参考。

在托卡马克装置中，离子回旋共振加热(ion cyclotron resonance heating, ICRH)引起的射频鞘会诱发一系列负面效应。数值模拟ICRH下的射频鞘，对控制芯部等离子体污染，延长天线和相关部件的材料寿命，提高波与等离子体的耦合效率有着重要意义。本项目采用数值计算方法，结合ICRH实验结果和射频鞘的理论，研究ICRH时存在高能电子/离子的射频鞘的结构特性，揭示鞘层电势和鞘层长度在不同等离子体参数和扰动电流源下的变化规律。然后根据基于Sigmund理论的经验公式计算杂质溅射产额；分析存在高能电子和磁场下的离子能量分布；考虑横越鞘层打到材料表面的能流；计算存在高能电子/离子情况下的鞘功率损耗。在解释ICRH中与射频鞘相关的实验现象基础上，探索控制高功率ICRH下杂质产生的有效措施，阐明存在高能电子下热流打到ICRH中天线相关部件表面增大的原因以及寻找减少鞘功率损耗的方法，为EAST天线优化和今后反应堆利用ICRH时的天线设计提供参考。受项目资助，在《Plasma Phys. Controlled Fusion》，《Phys. Plasmas》等杂志上共发表SCI收录论文八篇，其中项目负责人作为第一作者七篇。